The present inventive concepts relate to a high-electron-mobility transistor (HEMT) device, and more particularly, to a HEMT device that has a “normally off” characteristic.
In order to use as a transistor for a power device that obtains a high breakdown voltage and fast response speeds, a study on a high-electron-mobility transistor (HEMT) has been actively conducted. An HEMT device includes semiconductor layers with different electrical polarization characteristics, and a semiconductor layer with relatively great polarizability in the HEMT device may cause another semiconductor layer bonded heterogeneously thereto to have two-dimensional electron gas (2 DEG), i.e., a gas of electrons free to move in two dimensions but tightly confined in the third dimension. The 2 DEG may serve as a channel between a drain electrode and a source electrode, and currents flowing in the channel may be controlled by a bias voltage applied to a gate electrode. A conventional HEMT device, e.g., an HEMT device using a heterogeneous junction by a group III-nitride semiconductor, has a “normally on” characteristic and has high power consumption due to such a normally on characteristic.